There is some code for Letters.app is on GitHub, but I don't think it got very far and the last commit was two years ago. https://github.com/ccgus/letters http

There is some code for Letters.app is on GitHub, but I don't think it got very far and the last commit was two years ago. https://github.com/ccgus/letters https://github.com/ccgus/letters I remember thinking at the time it sounded quite interesting, so it's a shame. I'm guessing the need for it evaporated with the improvements in Mail.app and the development of other native clients.